2020-22 KTM 250 - 390 Adventure Bike Build


Back from a 2.5 hour ride on my 390 Adv.  The fuel controller and header upgrades result in a very solid improvement...everywhere in the RPM range.  Sure, the upper range is stronger, no question, but so is the lower range. Very smooth and strong on acceleration, as well.  Gear choice is now much more flexible, which is great--easier to ride and more fun.  No hit to MPG; in fact, I saw a small increase, maybe because I'm able to run at in a higher gear, much of the time.  And note that I was running a Booster Plug, before this.  


I'd call these upgrades a win, by any and all standards.  Great job, Dave. 

Above is a 2020 KTM 390 Adventure.  After buying it and riding it stock, down the roads and out in the dirt and the bumps, I can honestly say it's a big dumb pig.  Slow and heavy.  Totally reminds me of buying the first Honda CRF 250 L, that came into Arizona, and developing it.

When I rode the 250L, outside of the dealership, I wanted to ask them to take it back and see if I could have my money back.  Thing was, I bought it because a great price point at $5000 or whatever it was then. I also knew, that after I figured out the performance kit for it, that it would be totally different. And it worked. That bike weighed 300 lbs and had 18 hp stock. We got some weight off and got the power to 26 and it was a whole new bike.  Honda sold a bunch of bikes and we sold a bunch of kits.

This new 390 KTM is the same kind of thing.  It's on the heavy side, but some weight can come off.  It feels odd and wrong, as far as ergonomics go. Especially for control in the dirt. But that can be fixed.  And finally it needs more power, get up and go and some reliability.  And we can definitely fix that.


     As we started taking apart this bike, we realized how heavy the battery was.  For about $100, you can loose a whole 6 lbs by going to a good lithium battery.  This is high centered weight you feel. It's a must do


     The people who design the best performance products ( us and just a few others ) know darn well to take measurements of stock componets first.  On a fuel injected bike, the fuel pressure is so, so critical to performance and even maintaining stock running condition.  The running pressure of the stock bike is 54 psi. If the pressure falls below this, then starting and acceleration will suffer.  The lower it goes, the worse performance gets.   


     The next big parameter, that's super critical to know, on a fuel injected bike, is the air / fuel ratio.  Now on this particular  bike, it has an Oxygen sensor welded in the head pipe to make what we call a "closed loop" injection system.  This means that the O2 sensor feeds back information to the ECU ( electronic control unit ). This means that the system tries to make adjustments to the fuel amount to the injector, so that the pre determined air/ fuel ratio is kept.

    In the case of this stock bike, the pre determined air/ fuel ratio, seems to be 14.7 :1.  That's what the gauge we hooked up to shows.   When you ride down the street, the gauge fluctuates a bit, but it centers around 14.7.

    When you crack the gas, there is a bit of an accelerator pump kick in in 1st and 2nd gear but not a lot.  It shoots to 13.5 :1 every once in awhile. Which is a bit richer to aid in the "get up and go", but then goes right back to 14.7.

    This is important to know. Because we need to know how far you can go with opening up exhaust and intake flow, before the ecu can't adjust anymore and the bike starts to lean out.

Now that a few parameters and notes, on how it's running are taken, lets go ride it.   The first thing you may notice, is that it's an odd feeling bike, when you are riding it. Especially offroad.


     You'll definitley want to remove the rubber inserts from the footpegs. That done by removing the bolt under the bottom of the peg.  Then at least you feet will be in a better position for using the foot controls.

     After that, you'll really be in a better riding position if you use these bar risers we have, to get the bars up higer and further back.  You can see the black piece sitting on the tank above, which is the bar riser we have for use with the stock handlebars.  These move the stock bars up 3/4" or 19mm and back 1.25" or 30mm.  For a small amount of money, this is a HUGE difference in comfort and control


     Now let's get back to the best stuff, which is making and improving power delivery.   You can see a dyno run of our bike in stock condition below.  It's the lower of the 2 lines on both of the graphs.   This is on the stock tires at 25 psi.  


                               AND THEN TALK ABOUT THE REST OF THE OPTIONS.

    The upper line, is just the addition of our end cap.  There is NO reason to spend over $100 to make this muffler good. Our end cap makes the stock muffler make as much power as any of the expensive aftermarket mufflers.  We know, we tried those too


ktm exhaust vs stock.jpeg
390 apart.jpeg

     So you can see our high flowing endcap with it's 1.5" outlet hole, versus the stock 7/8" hole, which is also confined for a length of 4".  That's a lot of restriction.  The stock muffler has a straight through 1 7/8" core, so with the new end cap, you can easily understand how any high dollar muffler, isn't going to breath any better than this.

     You just drill out the stock rivets and remove the stock cap. Then install ours with the supplied torx screws.

And it's the only exhaust on the market, including the stock one, that can use an optional spark arrestor.  These bikes go in the brush and trees in the offroad areas too, so why no one want's to help keep you from lighting your area on fire, is just mind boggling.

390 on.jpeg


No product

     Stock gearing is 15-45, and that is just to tall, for any kind of decent acceleration.   It's so much easier to switch the stock 15 tooth to a 14, than switch out the rear sprocket to a 48 or 49 tooth.    The front one, you can just change with the bike on the side stand.

     To change the rear, you'll have to buy a new chain.   The cost effectiveness and pure effectiveness,of just doing the front, makes it the final perfect addition.


     At least the 14 tooth was a good idea until the chain stretch was discovered.  After only 668 miles on the odometer, the chain stretch you see above was discovered .  You can see it's a whole half link. Now I'm not sure how much a chain should stretch in only 668 miles. Also It wasn't sissy riding, so that didn't help. 

     BUT. It does seem excessive and soon the sprocket teeth can't help but curl over.  SO, maybe going to a better quality chain is a good idea. Ans since you can use a longer one now, you may as well use a 48 tooth rear and just keep the 15 front.  The over all gearing ratio is the same as using a 14 front, at 3.2 :1, so you get the same great acceleration increase, but you also fix a weak link in the bike.

     We have the chain and sprocket set, as you see above, or you can just get the sprocket, below.  You will need a longer chain though.  You can use 116 or 118 links.  The 118 will make the rear suspension not so stiff though, as the swing arm length and hence the flex in the swing arm will be greater.  The increased flex makes the rear more supple over all bumps and pot holes.


     At this point it was tire time. I'm way more of an offroad guy than on road, and a lot of hills on my normal test route, I couldn't get up with the stock tires.

    I put some cost effective Shinko brand Trail adventure tires on it. They are the 805 and 804.  They are tubeless and I run 18 psi front and 20 psi rear, after some testing.

    They are as smooth on the road as the stock one, and so far have climbed all the hills the stock ones couldn't.

    For under $200 for both, I think it was a great choice and will use them again.  Plus they look manly tough

390 adjustable brake lever.jpeg

     The folding, adjustable levers became a ( must have ) one day, when I crashed one day and the brake lever broke off.

     The brake lever was already a pain, because you couldn't adjust it close enough to the grip for smaller hands, so better levers where already on the way.

    But when the stock lever broke so fast, these became a must.

     Seems you can find a lot of these things on ebay and amazon, but none of those ever fit right, if they fit at all.

    These levers are pretty good and look pretty cool.

No product

brake set furthest in.jpeg

Just to get an idea of how far these levers can come in, for smaller hands, this is the brake on the left and clutch on the right.

     The brake still stops before it hits fingers on the grips.

      The clutch has 4 mm of cable freeplay, so could even come in further with more freeplay

clucth sset furthest in and 4mm freeplay.jpeg


ktm 390 adventire ecu.jpeg

     Adding needed fuel to the 390 Adventure wasn't so easy at first.  The only 2 options, were an expensive ecu, that you you couldn't manipulate, or a cheaper ecu that never worked right no matter what we tried.     

     So we had to design our own programmer to fix the fueling problems.  And since the competition had already released their efforts, we knew what we had to beat.   And for less than half the price of the Coober ecu,  we beat them bad.

     Instead of writing all the info again, it easiest to go to this page to learn more.

ktm 390 afr.jpeg

     This easy to install programmer, is the only thing on the market, that will add a much needed accelerator pump circuit, to your bike.  With all this bike weighs, and not a lot of power, it needs all the help it can get, in the "get up and go department".   And this accelerator pump squirt, is what does it.

     You can also add all the fuel you want, to the bike, past about 6500 rpm, with a quick push of a button.

The video below shows installation, where to set the 6 different modes and help explain what they do

     Now that the exhaust is flowing better, and we have some much needed fuel, lets add some more air to the bike.  This one is easy and free. It's adds power, but doesn't add annoying sound.   Like the deep howl you get, from some open air box lids, during acceleration.

     And now, let's finally bring this whole thing together, as far as performance goes, and add the CERAMIC COATED  coober brand "de cat" header to it.   Why the Coober one, and not some others? Because the bikes run WAY better with the stock "pre muffler" box, and just a De cat header, than they do with a header that doesn't use the stock pre muffler.

    And if you had all the headers on the market, and tested back to back, you'd find the same thing. If you bypass the stock pre muffler box, the bike will not only be to loud for most people, but will feel real flat and sluggish, at lower throttle openings.  And this isn't something you can fix with even our fuel programmer.

    Our internally ceramic coated Coober header, runs the best by far, for response, drivability, overall power and even the great sound, when used with our end cap

No product

      So a good question is "what is ceramic coating?" , and "why would you care, or do it ?"   And those are good questions.

      A ceramic coating, pained or sprayed on something, gives it a thermal barrier.  And this keeps heat inside the pipe better, than no barrier at all


      And if you wonder, why you'd care at all, well look at the pic above.  The absolutely hottest part of the exhaust, and engine, is about 3/4 " or 19mm below the radiator.  So all this heat is just radiating up and boiling the radiator all the time.  So now you know why the fan is on all the time.  And the stock header, runs hotter than this new "de cat" header.


     Here you can see the coating, sprayed inside of the pipe (orange).

     It's an expensive deal if you do the outside, about $130.  The inside is expensive as well, but not as bad.

     You get the idea though.  It's a nice value added deal, that has merits and positive results.

     So if you wonder why our headers are more than if you buy them straight from coober, well now you know.

     It's less from us, than if you bought from them and tried to do


Ad just in case you are wondering if you HAVE to add fuel to your KTM 390 Adventure, when using a De-Cat header?  Well you can watch the video below.  End result is, you don't HAVE to, but this only applies to the Coober brand, ceramic coated header that we sell.  All others and other set ups, we don't know anything about.  You'd be on your own with them